I found a solution. Quick: For some reason when opening a go file using
go-mode, Emacs/eglot generates a "textDocument/didOpen" server message. Now
the correct reaction of a LS upon such a message in a chase where the file
actually did not change remains disputable:

https://github.com/golang/go/issues/50267
https://github.com/neovim/neovim/issues/16623

However, the gopls-team considered a "chatty" behavior of the language
server to be better anyhow. To always send diagnostics is now the default,
yet not released as of gopls 1.10.1

https://github.com/golang/tools/commit/ec743893cd01c9423aaae4513b092c4c4c06f0f4
https://groups.google.com/g/golang-checkins/c/tt8Ig_UsKtE

To use the yet unreleased feature from gopls@HEAD which works, follow

https://github.com/golang/tools/blob/master/gopls/doc/advanced.md#unstable-versions

This bug report may be closed, reported for reference.


Am So., 11. Dez. 2022 um 13:45 Uhr schrieb Johann Höchtl <
johann.hoechtl@gmail.com>:

> I dug deeper into the problem:
>
> * When I open a very small golang-project, eglot interconnects correctly
> with gopls
> * When I open a larger golang-project, eglot fails to communicate with
> gopls. In fact, it fails to direct gopls to load the project as gopls stays
> at a very small memory footprint.
>
> When I uninstall go-mode OR find-file-literally *.go and later enable
> eglot, gopls  is correctly "directed" to load the project, because memory
> consumption is much higher. In this case it also reports back to eglot
> "loading packages" and "finished loading packages".
>
> Sidenote: However I cannot interact any further with the LS as eglot
> doens't consider any buffer as managed:
>
> cl-no-applicable-method: No applicable method: eglot--managed-buffers, nil
> eldoc error: (jsonrpc-error No current JSON-RPC connection
> (jsonrpc-error-code . 32603) (jsonrpc-error-message . No current JSON-RPC
> connection))
> mouse-minibuffer-check: Minibuffer window is not active
>
> but I guess this is because the buffer has no mode eglot considers to be
> supported.
>
> Sidenote2: If I enable go-mode for this buffer (thus triggering
> eglot-ensure in .emacs) , a second gopls process is spawned yet without
> communication between eglot and gopls.
>